Method and apparatus for removing marine organisms from a submerged substrate

ABSTRACT

A method and apparatus for removing marine fouling from underwater substrates such as ships&#39; hulls ( 10 ). The method is characterized by the steps of first subjecting marine organisms such as barnacles to an electrical field of sufficent intensity to degrade the adhesive properties of the organisms to the substrate, and thereafter physically removing said organisms with the help of rotating brushes ( 16 ) or similar abrasive removal means. The apparatus is characterized in that it includes a remotely operated submarine ( 12 ) or other suitable transport means, such as a vehicle with a magnetized caterpillar track, having a forwardly mounted electrode ( 14 ) for imparting an electric field to the organisms together with abrasive removal means ( 16 ) mounted behind the electrode for removal of the organisms. A power source ( 18 ) is provided, having one pole ( 20 ) connected to substrate ( 10 ) and a second pole connected to electrode ( 14 ).

This application is a 371 of PCT/NO00/00146 filed May 2, 2000, whichclaims benefit to Provisional Application No. 60/133,030 filed May 7,1999.

TECHNICAL FIELD

This invention relates to the removal of marine fouling from structuresexposed to a marine environment, and in particular ships' hulls.

BACKGROUND ART

The fouling of underwater structures by marine organisms is a well-knownproblem. Both static structures such as oil platforms, and mobilestructures such as ships are affected. In the case of ships, theaccumulation of marine growth can drastically reduce a vessel's speedand increase fuel consumption. As a result, ships must be regularlyserviced to remove this growth. The servicing of ships, however, is veryexpensive, not only in terms of direct costs but also in lost revenueswhile the ship is idle. Consequently, increasing the speed with whichthis work is performed is critical.

Of the various types of organisms that comprise marine fouling, one ofthe post troublesome is the barnacle. This organism, which outwardlyresembles a mollusk, is actually a crustacean, of the class cirripedia.In its larval stage, the barnacle attaches itself headfirst to asubstrate such as a ship's hull, and thereafter constructs a shellcomposed of six calciferous plates. The animal attaches these plates tothe substrate with one of the most powerful adhesives known in nature,which makes removal of the shell extremely difficult. Barnacles areparticularly troublesome because these shells remain attached even afterthe animal is dead.

Various methods have been developed for killing marine growth, howeverthese methods do not address the problem of removing the organisms afterthey have been killed. U.S. Pat. Nos. 5,327,848; 5,2401,674; and5,593,636 disclose the use of heat for killing zebra mussels. Thesepatents disclose that the use of temperatures in the order of 35-45degrees Centigrade is sufficient to achieve adequate mortality. U.S.Pat. No. 5,804,065 discloses the use of a low-level electric field tokill marine growth. This patent teaches that subjecting zebra mussels toa field having a power density between about 3,500 to 50,000microwatts/cubic centimeter for a time interval of about 24 to 72 hoursis sufficient to achieve adequate mortality. These patents do notdisclose, however, any effect on the adhesive properties of barnacleshells to a substrate, nor provide a means for the removal of suchshells. In particular, the time intervals disclosed by U.S. Pat. No.5,804,065 demonstrates that the technique disclosed therein is aimed atstopping the reproduction and propagation of the organisms, and isconsequently unsuitable for the efficient cleaning of hulls or othersubstrates.

OBJECTS AND ADVANTAGES

It is therefore an object of the current invention to provide anapparatus and method for removing marine fouling from a substrate, inparticular marine organisms such as barnacles, which attach to thesubstrate with the help of a natural adhesive. It is a further object ofthe invention to provide an apparatus and method that improves the speedand efficiency with which marine fouling can be removed. Still furtherobjects and advantages will become apparent from a consideration of theensuing description and drawings.

DISCLOSURE OF THE INVENTION

The present invention is directed to an improved method and apparatusthat takes a novel approach for removing marine fouling from underwaterstructures such as ships' hulls. The method is characterized by thesteps of first subjecting marine organisms such as barnacles to anelectrical field of sufficient intensity to degrade the adhesiveproperties of the organisms to a substrate, and thereafter physicallyremoving said organisms with the help of rotating brushes or similarabrasive removal means. The apparatus is characterized in that itincludes a remotely operated submarine or other suitable transportmeans, such as a vehicle with a magnetized caterpillar track, having aforwardly mounted electrode for imparting an electric field to theorganism=together with abrasive removal means mounted behind theelectrode for removal of the organisms.

BRIEF DESCRIPTION OF THE DRAWINGS

Details of the invention are described in connection with theaccompanying figures, wherein:

FIG. 1 is a side elevational view of a remotely operated submarine witha forwardly mounted electrode and brush arrangement in operation with aship.

FIG. 2 is an enlarged perspective view of the remotely operatedsubmarine from FIG. 1.

FIG. 3 is an enlarged elevational view of the electrode mounted on theremotely controlled submarine, showing lines of current impinging uponmarine organisms.

FIG. 4 is an enlarged perspective view of the remotely operatedsubmarine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the figures there is shown an apparatus for removal ofmarine fouling from a ship with a hull 10. The apparatus comprises aremotely controlled submarine 12 to which is connected a forwardlymounted electrode 14. Rotating brushes 16 are mounted on submarine 12immediately behind electrode 14. The apparatus is connected to a powersource 18, with a first pole 20 terminating at hull 10 and a second poleterminating at electrode 14. As depicted in FIG. 3, an electric currentis caused to flow through a marine organism 22 when electrode 14 isbrought within proximity to hull 10.

Empirical results have demonstrated that an electrical current ofsufficient intensity will significantly reduce the adhesion of marineorganisms such as barnacles to a substrate, such as hull 10. As aresult, brushes 16 are capable of removing the organisms much moreeasily than is the case with known methods.

The mechanism that affects the adhesion of the barnacles is notprecisely known. One possible explanation is that electrical resistanceat the contact point between the barnacle and the substrate causes alocalized heating, which in turn degrades the holding properties of thenatural adhesive with which the barnacle attaches itself. Test resultsaccording to the following tables have demonstrated that the applicationof heat produces results similar to those observed with electricalcurrents. The test involved measuring the force required to physicallyremove randomly selected from a metallic substrate.

TABLE 1 No heat applied Test barnacle Measured force 1 1.0 kg 2 1.5 kg 32.5 kg 4 2.5 kg 5 1.0 kg 6 1.5 kg average 1.66 kg

TABLE 2 250° C. Test barnacle Time sec force 1 3 0.1 kg 2 3 0.0 kg 3 30.5 kg 4 3 0.5 kg 5 3 0.1 kg 6 3 0.0 kg average 0.2 kg

TABLE 3 100° C. Test barnacle Time sec force 1  2 1.5 kg 2 10 0.1 kg 310 0.5 kg

Another possible explanation for the observed phenomenon, which may infact work together with heat to produce the observed results, is thathigh velocity tons or bubbles produced by electrolysis attack theintegrity of the adhesive.

In the preferred embodiment of the invention, an AC power source isemployed in which opposite poles are attached to hull 10 and electrode14 respectively. It is understood, however, that a DC power source couldbe employed. In another embodiment, electrode 14 could be replaced byone or more pairs of oppositely charged electrodes spaced relative toone another so as to create an electric field of desired intensity,which electric field could be placed in proximity to the organisms toachieve the required effect. It is further is understood that while thepreferred embodiment envisions utilizing a remotely controlled submarineto transport electrode 14 and brushes 16 along hull 10, other transportmeans could equally be employed.

What is claimed is:
 1. Method for the removal of marine organisms from asubmerged substrate, comprising the steps of first subjecting saidorganisms to an electric current of sufficient intensity to degrade theadhesive properties of said organisms and thereafter physically removingsaid organisms with an abrasive removal means.
 2. Method of claim 1,wherein said organisms are subjected to said electric current by thesteps of connecting a first pole of a power source to said substrate,connecting a second pole of said power source to an electrode, andthereafter bringing said electrode within sufficient proximity of saidsubstrate so as to create an electrical current flowing through saidorganisms.
 3. Method of claim 2, wherein said electrode is mounted on anunderwater transport means, and wherein said abrasive removal means ismounted on said underwater transport means behind said electrode. 4.Method of claims 3, wherein said underwater transport means is aremotely controlled submarine and wherein said abrasive removal meansare rotating brushes.
 5. Apparatus for removing marine organisms from asubmerged substrate, comprising: a) An underwater transport means b) anelectrode mounted on said underwater transport means c) abrasive removalmeans mounted to said underwater transport means behind said electroded) a power source with a first pole connected to said substrate and asecond pole connected to said electrode, said power source being ofsufficient strength to create an electric current flowing through saidorganisms, when said electrode is brought within close proximity to saidsubstrate, of sufficient intensity to degrade the adhesive properties ofsaid organisms.
 6. Apparatus according to claim 5, wherein saidunderwater transport means is a remotely controlled submarine andwherein said abrasive removal means are rotating brushes.